阅读说明：本技术 乙烯丙烯酸酯橡胶组合物及其成型品 (ethylene acrylate rubber composition and molded article thereof ) 是由 大谷圭太 于 2018-10-17 设计创作，主要内容包括：本发明提供一种成型及交联之后均衡性良好地具有耐油性、耐热性及耐水解性三者的乙烯丙烯酸酯橡胶组合物以及由该乙烯丙烯酸酯橡胶组合物的交联物构成的成型品。乙烯丙烯酸酯橡胶组合物的特征在于,包含：100质量份乙烯丙烯酸酯橡胶；10～50质量份的SP值为7以上的增塑剂；以及0.05～30质量份的选自脂肪族多元伯胺及其衍生物的交联剂,SP值小于7的增塑剂的含量小于0.1质量份。并且,提供由该乙烯丙烯酸酯橡胶组合物的交联物构成的成型品。(The invention provides an ethylene acrylate rubber composition which has oil resistance, heat resistance and hydrolysis resistance in a well-balanced manner after molding and crosslinking, and a molded article composed of a crosslinked product of the ethylene acrylate rubber composition. The ethylene acrylate rubber composition is characterized by comprising: 100 parts by mass of an ethylene acrylate rubber; 10 to 50 parts by mass of a plasticizer having an SP value of 7 or more; and 0.05-30 parts by mass of a cross-linking agent selected from aliphatic poly-primary amines and derivatives thereof, wherein the content of the plasticizer with the SP value of less than 7 is less than 0.1 part by mass. Also disclosed is a molded article comprising a crosslinked product of such an ethylene acrylate rubber composition.)

1. An ethylene acrylate rubber composition, comprising:

100 parts by mass of an ethylene acrylate rubber;

10 to 50 parts by mass of a plasticizer having an SP value of 7 or more; and

0.05 to 30 parts by mass of a crosslinking agent selected from aliphatic poly-primary amines and derivatives thereof,

The content of the plasticizer having an SP value of less than 7 is less than 0.1 part by mass.

2. The ethylene acrylate rubber composition according to claim 1,

Comprises 20 to 150 parts by mass of carbon black and 20 to 150 parts by mass of at least one of silica.

3. The ethylene acrylate rubber composition according to claim 1 or 2, wherein,

The plasticizer with the SP value of more than 7 is more than one selected from polyether ester plasticizer, trimellitate plasticizer, pyromellitic ester plasticizer and hydrogenated hydrocarbon plasticizer.

4. A molded article comprising a crosslinked product of the ethylene acrylate rubber composition according to any one of claims 1 to 3.

5. The molded article according to claim 4, which is a sealing material.

Technical Field

The present invention relates to an ethylene acrylate rubber composition and a molded article thereof.

Background

Acrylic rubber has excellent oil resistance and heat resistance and is less expensive than fluororubber, and is therefore frequently used as sealing products such as oil seals, gaskets, O-rings, and the like. However, acrylic rubber is susceptible to hydrolysis reaction with water (acid/alkali), and is inferior to other synthetic rubbers such as nitrile rubber and fluororubber in water resistance.

However, various engine oils including engine oil are present around many automobile engines using a sealing material (acrylic rubber is used). These engine oils may contain a slight amount of water due to condensation, rain, and the like generated by temperature changes during operation and stop of the engine. Further, in the engine part, moisture generated by the combustion of the fuel may be mixed into the engine oil.

Therefore, the sealing material using the acrylic rubber is exposed to moisture in a use environment, and is degraded by hydrolysis, and as a result, the sealing function may not be maintained.

Therefore, as a method of improving the hydrolysis resistance of acrylic rubber, ethylene acrylate rubber is used as a rubber having higher hydrolysis resistance than acrylic rubber and having a similar chemical structure. However, the ethylene acrylate rubber has a problem that the oil resistance is slightly inferior to that of the acrylic rubber.

Various attempts to improve the properties by adding a third component to an ethylene acrylate rubber composition are known. For example, in patent document 1, heat resistance and cold resistance are simultaneously achieved by adding an ester compound of a specific chemical structure.

Disclosure of Invention

Problems to be solved by the invention

However, in the ethylene acrylate rubber composition, a technique of simultaneously achieving oil resistance, heat resistance and hydrolysis resistance after molding and crosslinking is not known.

The present invention has been accomplished in view of such circumstances. That is, an object of the present invention is to provide an ethylene acrylate rubber composition having oil resistance, heat resistance and hydrolysis resistance in a well-balanced manner after molding and crosslinking, and a molded article comprising a crosslinked product of the ethylene acrylate rubber composition.

Means for solving the problems

The present inventors have found that by adding appropriate amounts of a plasticizer and a crosslinking agent suitable for an ethylene acrylate rubber, oil resistance and hydrolysis resistance can be simultaneously achieved while heat resistance is maintained after molding and crosslinking, and have completed the present invention. The present invention has the following structure.

The ethylene acrylate rubber composition of the present invention comprises: 100 parts by mass of ethylene acrylate rubber, 10-50 parts by mass of a plasticizer having an SP value of 7 or more, and 0.05-30 parts by mass of a crosslinking agent selected from aliphatic poly-primary amines and derivatives thereof, wherein the content of the plasticizer having an SP value of less than 7 is less than 0.1 part by mass.

also, the ethylene acrylate rubber composition of the present invention preferably contains 20 to 150 parts by mass of at least one of carbon black and 20 to 150 parts by mass of silica.

In the ethylene acrylate rubber composition of the present invention, the plasticizer having an SP value of 7 or more is preferably one or more selected from the group consisting of polyether ester plasticizers, trimellitate ester plasticizers, pyromellitic ester plasticizers and hydrogenated hydrocarbon plasticizers.

The molded article of the present invention is composed of a crosslinked product of the ethylene acrylate rubber composition. Further, the molded article of the present invention is preferably a sealing material.

ADVANTAGEOUS EFFECTS OF INVENTION

The ethylene acrylate rubber composition of the present invention has oil resistance, heat resistance and hydrolysis resistance in a well-balanced manner after molding and crosslinking. The molded article of the present invention has oil resistance, heat resistance and hydrolysis resistance in a well-balanced manner.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail. However, the scope of the present invention is not limited to the embodiments described below.

The ethylene acrylate rubber composition of the present invention comprises an ethylene acrylate rubber, a plasticizer having an SP value of 7 or more, and a crosslinking agent selected from aliphatic poly-primary amines and derivatives thereof. Hereinafter, each component constituting the ethylene acrylate rubber composition of the present invention will be described.

(ethylene acrylic acid ester rubber)

Ethylene acrylate rubber is also known as ethylene acrylate rubber or AEM. The ethylene acrylate rubber is a polymer obtained by copolymerizing ethylene and an alkyl acrylate as main monomer components and a crosslinkable monomer having a crosslinkable group, and is preferably a terpolymer.

Examples of the alkyl acrylate include alkyl acrylates having 1 to 20 carbon atoms in the alkyl group. Specifically, there are methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, tert-butyl acrylate, propyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, stearyl acrylate and the like. Among them, methyl acrylate, ethyl acrylate and n-butyl acrylate are preferable, and methyl acrylate is more preferable.

As the ethylene acrylate rubber, an ethylene acrylate rubber having a crosslinkable group crosslinked by an aliphatic polyvalent primary amine or a derivative thereof is used. Therefore, the crosslinkable group of the crosslinkable monomer constituting the ethylene acrylate rubber is required to be a crosslinkable group crosslinked by an aliphatic polyamine or a derivative thereof. Examples of such crosslinkable groups include carboxyl groups, epoxy groups, and halogen groups. Among them, the crosslinkable group is preferably a carboxyl group.

Examples of the crosslinkable monomer having a carboxyl group include monoalkyl esters of unsaturated dicarboxylic acids such as methyl, ethyl, propyl, isopropyl, n-butyl, and isobutyl esters of maleic acid, fumaric acid, itaconic acid, and citraconic acid, and unsaturated monocarboxylic acids such as acrylic acid and methacrylic acid. The crosslinkable monomer having these crosslinkable groups is used in the ethylene acrylate rubber at a copolymerization ratio of about 0.5 to 10 mass%.

Examples of commercially available products of the ethylene acrylate rubber include Vamac (registered trademark) G and Vamac GLS manufactured by DuPont DOW Elastomer (DuPont DOW Elastomer). These ethylene acrylate rubbers may be used using one or a mixture of a plurality of rubbers.

(plasticizer)

the present inventors speculate that it is important to select an appropriate plasticizer in order to achieve oil resistance, heat resistance, hydrolysis resistance and processability of the ethylene acrylate rubber composition after molding and crosslinking in a well-balanced manner. That is, it is considered that the oil resistance of the ethylene acrylate rubber is supplemented to be particularly important because the ethylene acrylate rubber has excellent compatibility with the ethylene acrylate rubber, can be stably present in the composition, and is appropriately immiscible with both oil and water.

The SP value is a parameter used for evaluating the compatibility of the two components. The SP value refers to a Solubility Parameter (Solubility Parameter) known as a measure representing intermolecular forces. It is known that the smaller the difference between the SP values of the two components, the higher the compatibility.

Therefore, an attempt was made to select a plasticizer with the SP value as a clue. The SP value of the ethylene acrylate rubber depends on the grade, and therefore cannot be determined as a clear numerical value, but is estimated to be 8 or more. Therefore, various plasticizers having different SP values were used to prepare a composition containing ethylene acrylate rubber, and the molded article after molding and crosslinking was evaluated for oil resistance, heat resistance and hydrolysis resistance. As a result, it was found that a plasticizer having an SP value of 7 or more is effective. More preferably, the SP value of the plasticizer is 8 or more.

The kind of the plasticizer having an SP value of 7 or more is preferably at least one selected from the group consisting of polyether ester plasticizers, trimellitate ester plasticizers, pyromellitic ester plasticizers and hydrogenated hydrocarbon plasticizers. Among them, trimellitate plasticizers having more excellent kneading processability are preferable.

Specific examples of the polyether ester plasticizer include Adekasizer RS735 (manufactured by ADEKA Co., Japan) and Adekasizer RS700 (manufactured by ADEKA Co., Japan).

Specific examples of the trimellitate plasticizer include tri (2-ethylhexyl) trimellitate, tri-n-octyl trimellitate, triisodecyl trimellitate, triisononyl trimellitate, and mixed higher alcohol trimellitates.

Specific examples of the pyromellitic acid ester plasticizer include tetra (2-ethylhexyl) pyromellitate, tetra-n-octyl pyromellitate, and higher alcohol pyromellitic acid ester.

Specific examples of the hydrogenated hydrocarbon plasticizer include Durasyn series manufactured by INEOS.

10 to 50 parts by mass of a plasticizer having an SP value of 7 or more is blended with 100 parts by mass of an ethylene acrylate rubber. The content of the plasticizer having an SP value of 7 or more is preferably 10 to 30 parts by mass, and more preferably 10 to 20 parts by mass. When the plasticizer having an SP value of 7 or more is contained in the above amount, processability, heat resistance, oil resistance and hydrolysis resistance can be satisfied in a well-balanced manner.

As the plasticizer, a plasticizer having an SP value of 7 or more and a plasticizer having an SP value of less than 7 may be used in combination, but there is a risk that the plasticizer having an SP value of less than 7 bleeds out to lower the processability. Therefore, when both are used in combination, the content of the plasticizer having an SP value of less than 7 is less than 0.1 part by mass relative to 10 to 50 parts by mass of the plasticizer having an SP value of 7 or more.

(crosslinking agent)

As described above, as the ethylene acrylate rubber, an ethylene acrylate rubber crosslinked by an aliphatic polyvalent primary amine or a derivative thereof is used. Therefore, as the crosslinking agent, a crosslinking agent selected from aliphatic poly-primary amines and derivatives thereof is used.

Examples of the aliphatic polyvalent primary amine which can be used as a crosslinking agent include aliphatic polyamines such as hexamethylenediamine, N' -dicinnamoldiene-1, 6-hexamethylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, ethylenediamine and 1, 4-diaminobutane.

Examples of the derivative of the aliphatic polyvalent primary amine include hexamethylenediamine carbamate and the like. These aliphatic polyvalent primary amines or derivatives thereof may be used alone, or two or more of them may be used in combination.

The crosslinking agent selected from the group consisting of aliphatic polyvalent primary amines and derivatives thereof may be incorporated in an amount of 0.05 to 30 parts by mass per 100 parts by mass of the ethylene acrylate rubber. The amount of the crosslinking agent is preferably 0.1 to 10 parts by mass, more preferably 0.3 to 1 part by mass.

(crosslinking accelerator)

In addition to the crosslinking agent, a crosslinking accelerator may be used in combination. As the crosslinking accelerator, an alkaline crosslinking accelerator is preferably used in combination. As the basic crosslinking accelerator, a guanidine compound, 1, 8-diazabicyclo [5.4.0] undec-7-ene (DBU), 1, 5-diazabicyclo [4.3.0] nonene-5, and the like can be used. Commercially available products include Vulcofac ACT55 manufactured by Safic Alcan corporation.

the crosslinking accelerator is preferably added in an amount of 0.05 to 20 parts by mass, more preferably 0.1 to 10 parts by mass, based on 100 parts by mass of the ethylene acrylate rubber.

The ethylene acrylate rubber composition preferably contains 20 to 150 parts by mass of at least one of carbon black and 20 to 150 parts by mass of silica per 100 parts by mass of the ethylene acrylate rubber.

(carbon Black)

Carbon black may be blended to reinforce the ethylene acrylate rubber composition. The type of carbon black is not particularly limited, and examples thereof include carbon blacks such as SRF, GPF, FEF, HAF, MAF, ISAF, SAF, FT, and MT, and MAF and SRF can be preferably used. The carbon black may be used alone or in combination of two or more. Commercially available products include Seast G-S, a trade name of carbon corporation of east China sea, Japan.

Preferably, 20 to 150 parts by mass of carbon black is blended with 100 parts by mass of the ethylene acrylate rubber. When the content of the carbon black is less than 20 parts by mass, it may be difficult to maintain the tensile strength of the ethylene acrylate rubber. When the content of carbon black is more than 150 parts by mass, kneading processability and moldability may be difficult to achieve. The content of carbon black is more preferably 30 to 100 parts by mass.

(silica)

In order to reinforce the ethylene acrylate rubber composition, silica may be blended. Specific examples of the silica include precipitated silica, colloidal silica, vapor-phase silica, and organic silica sol. Among them, precipitated silica is preferable. Examples of commercially available precipitated SILICA include Nipsil series produced by TOSOH SILICA K.K.Japan. Examples of commercially available colloidal silica include Snowtex series manufactured by Nissan chemical industries, Inc. Further, commercially available products of fumed silica include, for example, AEROSIL series produced by AEROSIL corporation of Japan. Examples of commercially available products of the organic silica sol include Snowtex series produced by Nissan chemical industries, Ltd.

Preferably, the silica is contained in an amount of 20 to 150 parts by mass per 100 parts by mass of the ethylene acrylate rubber. When the content of silica is less than 20 parts by mass, it may be difficult to maintain the tensile strength of the ethylene acrylate rubber. When the content of silica is more than 150 parts by mass, kneading processability and moldability may be difficult to achieve. The content of silica is more preferably 20 to 80 parts by mass.

In addition to the above components, if necessary, known compounding agents such as processing aids, reinforcing agents, fillers, acid acceptors, antioxidants, and stabilizers may be added to the ethylene acrylate rubber composition as appropriate. For example, there are processing aids such as stearic acid, and acid acceptors such as zinc oxide and magnesium oxide.

(crosslinked molded article of ethylene acrylate rubber composition)

In order to produce a crosslinked molded article from an ethylene acrylate rubber composition, a predetermined crosslinking agent, crosslinking accelerator, and the like are added to an ethylene acrylate rubber to prepare an ethylene acrylate rubber composition, and then molding and crosslinking are performed. The order of the molding step and the crosslinking step of the ethylene acrylate rubber composition is not particularly limited, and may be selected according to the shape of the member. The molding step may be performed before the crosslinking step, the crosslinking step may be performed before the molding step, or the molding step and the crosslinking step may be performed simultaneously.

As a mixer used for preparing the uncrosslinked ethylene acrylate rubber composition (rubber compound), known mixers such as a single-screw extruder, a twin-screw extruder, a roll, a banbury mixer, a kneader, and a high-shear internal mixer can be used. The method or the order of adding the components constituting the ethylene acrylate rubber composition to the kneader is not particularly limited.

The method for molding the molded article of the ethylene acrylate rubber composition is not particularly limited. Any method such as compression molding, injection molding, extrusion molding, and transfer molding can be used.

The crosslinking step for crosslinking the uncrosslinked ethylene acrylate rubber composition may be performed in one step, or may be performed in two steps of primary crosslinking and secondary crosslinking. By performing the secondary crosslinking after the primary crosslinking is performed, the crosslinking can be surely performed to the inside. The crosslinking conditions are generally carried out by pressure crosslinking at about 150 to 230 ℃ for about 0.5 to 30 minutes. When the secondary crosslinking is carried out, it is usually carried out by oven heating at about 150 to 250 ℃ for about 0.5 to 24 hours.

Molded articles formed from crosslinked products of ethylene acrylate rubber compositions are widely used in various fields such as transportation equipment such as automobiles, general-purpose equipment, electronic and electrical equipment, building parts, and hoses. In particular, the sealing material is useful as a sealing material such as a gasket, an O-ring, a seal, an oil seal, or a bearing seal.